Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$96.71	5.617%	$102.1422	$102.14	$102.15	$102.10
Purchase #2	$96.79	5.547%	$102.1589	$102.16	$102.15	$102.20
Purchase #3	$231.64	6.140%	$245.8627	$245.86	$245.85	$245.90
Purchase #4	$45.46	6.282%	$48.3158	$48.32	$48.30	$48.30
Purchase #5	$174.61	9.297%	$190.8435	$190.84	$190.85	$190.80
Purchase #6	$5.83	5.369%	$6.143	$6.14	$6.15	$6.10
Purchase #7	$96.59	3.579%	$100.047	$100.05	$100.05	$100.00
7 purchase totals =	$747.63		$795.5131	$795.51	$795.50	$795.40